Hard carbon negative electrode material derived from biomass

Abstract

The invention discloses a biomass-derived hard carbon negative electrode material as well as a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. The preparation method comprises the following steps: firstly carrying out pre-carbonization treatment on konjaku flour, then carrying out ball milling, acid treatment and drying, and finally, carrying out high-temperature calcination to prepare the hard carbon material. The preparation process is simple to operate, assistance of soft and hard templates and assistance of a surfactant and a pore-forming agent are not needed, and the prepared biomass-derived hard carbon assembled half-cell has good electrochemical performance and has the reversible capacity of 301.5 mAh / g under the current density of 30 mA / g. In addition, the konjaku flour which is artificially planted in a large area is used as the raw material, the reproducibility is high, the konjaku flour is easy to obtain, the cost is low, and the artificially planted organism is converted into a high-added-value product.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a hard carbon negative electrode material derived from biomass, and a preparation method and application thereof. Background Art

[0002] Sodium ion batteries have good low temperature performance and safety performance, and are most likely to replace lithium ion batteries and be commercially applied. At present, the relative scarcity of lithium resources and the increase in prices have made the development of a new generation of energy storage batteries a top priority. Compared with lithium, sodium has a higher content on the earth, is widely distributed, and the raw materials are more convenient to obtain. At the same time, sodium and lithium have similar physical and chemical properties, so sodium ion batteries are most likely to be used in secondary battery technology for large-scale energy storage systems. Because sodium ions have a larger ionic radius than ions, they cannot form a stable thermodynamic structure in graphite. Therefore, graphite, a lithium ion negative electrode material, cannot be used in sodium ion batteries, and a large interlayer spacing negative electrode material is required as a sodium ion battery negative electrode. Hard carbon, as a relatively difficult to graphitize carbon material, has an interlayer spacing of more than 0.37nm, making it an ideal material for the negative electrode of sodium ion batteries. Currently, the sources of biomass hard carbon materials reported are mainly coconut shells, starch, glucose, straw, etc. The hard carbons prepared from these biomass as carbon sources all show low coulombic efficiency, poor cycle stability and rate performance. Some of these biomass raw materials are relatively expensive and have a long growth cycle, making them unsuitable for preparing hard carbon materials. At the same time, a large amount of waste will be generated during the processing and preparation of some biomass materials, causing great pollution to the environment. This article uses konjac flour as a carbon source and prepares its hard carbon material through a simple preparation process, which greatly reduces the preparation time and cost. In addition, my country's planting area exceeds 10 million mu, and its output accounts for more than 70% of the world's total output. Therefore, using konjac flour to prepare carbon materials has price and output advantages. Summary of the invention

[0003] The purpose of the present invention is to provide a konjac flour-derived hard carbon for use as a negative electrode material for a sodium ion battery, which has a quick and simple preparation method, excellent electrochemical performance, and relatively considerable specific capacity and cycle performance.

[0004] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a biomass-derived hard carbon negative electrode material comprises the following steps: S1, pre-carbonizing konjac flour to generate pre-carbonized material; S2, after the pre-carbonized material is cooled, it is subjected to ball milling, acid leaching, water washing and drying to obtain a hard carbon material precursor; S3, calcining the hard carbon material precursor at high temperature to obtain the hard carbon negative electrode material.

[0005] Furthermore, in step S1, the pre-carbonization temperature is 200°C-800°C, and the time is 60min-300min.

[0006] Furthermore, in step S2, the mass ratio of ball milling beads to pre-carbonized material is 60:1-10:1, the ball milling time is 2h-24h, and after ball milling, the material is sieved through a 300-mesh screen.

[0007] Furthermore, in step S2, the acid leaching temperature is 25°C-100°C, and the time is 1h-24h; the acid used is at least one of hydrochloric acid, nitric acid, acetic acid, and phosphoric acid, and the concentration is 0.1-12 mol / L.

[0008] Furthermore, in step S3, the heating rate is 1-10°C / min, the calcination temperature is 800-1500°C, and the calcination time is 30min-600min.

[0009] The hard carbon negative electrode material derived from biomass is prepared by the method described above.

[0010] Application of biomass-derived hard carbon negative electrode material prepared by the method as described above in sodium ion batteries.

[0011] The beneficial effects of the present invention are: the preparation process is simple to operate, and no soft or hard template assistance, surfactant or pore-forming agent assistance is required. The prepared biomass-derived hard carbon assembled half-cell has good electrochemical performance and a reversible capacity of 301.5 mAh / g at a current density of 30 mA / g. In addition, the present invention uses konjac flour grown artificially on a large scale as raw material, which is highly renewable, easy to obtain, and low in cost, and realizes the conversion of artificially grown organisms into high value-added products. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the TGA diagram of konjac flour in Example 1 under argon atmosphere.

[0013] Figure 2 XRD patterns of hard carbon derived from konjac under different annealing conditions in Examples 1-3.

[0014] Figure 3 These are the Raman images of the hard carbon materials prepared at different annealing temperatures in Examples 1-3.

[0015] Figure 4 This is the first effect diagram of konjac-derived hard carbon of Examples 1-3.

[0016] Figure 5 These are the electrochemical diagrams of konjac-derived hard carbon at different rates in Examples 1-3.

[0017] Figure 6 These are SEM images of konjac-derived hard carbons of Examples 1-3. DETAILED DESCRIPTION

[0018] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0019] Example 1 S1: 5 g of konjac flour was placed in an alumina crucible, which was then placed in a tube furnace and an inert gas was introduced for a certain period of time.

[0020] S2: The material was pre-carbonized in a tube furnace from room temperature to 500 °C for 2 h.

[0021] S3: The obtained material was placed in a 100 ml ball milling jar at a material mass: ball milling beads ratio of 1:30, and ethanol was added as a dispersant and ball milled at 500 rpm for 12 h.

[0022] S4: The ball-milled material was treated with 0.5 mol / L nitric acid for 12 h.

[0023] S5: The dried material is placed in an alumina crucible carrier and heated from room temperature to 1300° C. in a nitrogen atmosphere and kept at this temperature for 2 hours for high temperature calcination.

[0024] S6: The high-temperature calcined materials are mixed in a mass ratio of 80:10:10 (hard carbon: Super P: PVDF), and stirred evenly to form a slurry.

[0025] S7: Use a 200mm scraper to evenly spread the slurry on the aluminum foil, and then dry it in a vacuum drying oven at 100°C. After drying, use a cutting machine (MSK-T10) to cut circular electrodes with a diameter of 14mm, weigh them, and calculate the mass of active substances to be 1.2~1.4mg.

[0026] The electrochemical performance of the konjac hard carbon material prepared in this example was tested: S1: Use sodium metal as the counter electrode and the electrolyte is 1 mol / L NaPF 6 in DME. The separator is glass fiber (GF / C), and C2032 button cells are assembled in a glove box filled with argon (Ar). The charge and discharge performance tests are carried out using the battery test system of Xinwei Electronics Co., Ltd.

[0027] S2: Button battery test voltage range is 0~3V, and 300mAh g -1 The current density was 1C and tests were conducted at 0.1C, 0.2C, 0.5C and 1C.

[0028] In this example, the material has a 241 mAh g -1The reversible capacity and ICE of 64% and 241 mAh g at 0.1C, 0.2C, 0.5C, and 1C rates are -1 , 136mAh g -1 , 57mAh g -1 , 36mAh g -1 reversible specific capacity.

[0029] Example 2 S1: 5 g of konjac flour was placed in an alumina crucible, which was then placed in a tube furnace and an inert gas was introduced for a certain period of time.

[0030] S2: The material is pre-carbonized in a tube furnace from room temperature to 300 °C for 2 h S3: The obtained material was placed in a 100 ml ball milling jar at a ratio of material mass to ball milling beads = 1:40, and ethanol was added as a dispersant and ball milled at 500 rpm for 12 h.

[0031] S4: The ball-milled material was treated with 1 mol / L nitric acid for 12 h.

[0032] S5: The dried material is placed in an alumina crucible carrier and heated from room temperature to 1100° C. in a nitrogen atmosphere and kept at this temperature for 2 hours for high temperature calcination.

[0033] S6: The high-temperature calcined materials are mixed in a mass ratio of 80:10:10 (hard carbon: Super P: PVDF), and stirred evenly to form a slurry.

[0034] S7: Use a 150mm scraper to evenly spread the slurry on the aluminum foil, and then dry it in a vacuum drying oven at 80°C. After drying, use a cutting machine (MSK-T10) to cut circular electrodes with a diameter of 16mm, weigh them, and calculate the mass of active substances to be 1.2~1.4mg.

[0035] The electrochemical performance of the konjac hard carbon material prepared in this example was tested: S1: Use sodium metal as the counter electrode and the electrolyte is 1 mol / L NaPF 6 in DEGDME. The separator is glass fiber (GF / D), and C2032 button cells are assembled in a glove box filled with argon (Ar). The charge and discharge performance tests are carried out using the battery test system of Xinwei Electronics Co., Ltd.

[0036] S2: Button battery test voltage range is 0~3V, and 300mAh g -1 The current density was 1C and tests were conducted at 0.1C, 0.2C, 0.5C and 1C.

[0037] In this example, the material has a capacity of 271 mAh g under the test condition of 0.1C. -1 The reversible capacity and ICE of 70% and 271 mAh g at the rates of 0.1C, 0.2C, 0.5C, and 1C -1 , 246mAh g -1 , 147mAh g -1 、89mAhg -1 reversible specific capacity.

[0038] Example 3 S1: 5 g of konjac flour was placed in an alumina crucible, which was then placed in a tube furnace and an inert gas was introduced for a certain period of time.

[0039] S2: The material is pre-carbonized in a tube furnace from room temperature to 500°C for 2 hours S3: The obtained material was placed in a 100 ml ball milling jar at a ratio of material mass to ball milling beads = 1:50, and ethanol was added as a dispersant and ball milled at 500 rpm for 24 hours.

[0040] S4: The ball-milled material was added with 0.5 mol / L hydrochloric acid for treatment for 12 h.

[0041] S5: The dried material is placed in an alumina crucible carrier and heated from room temperature to 900° C. in a nitrogen atmosphere and kept at this temperature for 2 hours for high temperature calcination.

[0042] S6: The high-temperature calcined materials are mixed in a mass ratio of 80:10:10 (hard carbon: Super P: PVDF), and stirred evenly to form a slurry.

[0043] S7: Use a 200mm scraper to evenly spread the slurry on the aluminum foil, and then dry it in a vacuum drying oven at 100°C. After drying, use a cutting machine (MSK-T10) to cut circular electrodes with a diameter of 14mm, weigh them, and calculate the mass of active substances to be 1.2~1.4mg.

[0044] The electrochemical performance of the konjac hard carbon material prepared in this example was tested: S1: Use sodium metal as the counter electrode and the electrolyte is 1 mol / L NaPF 6 in DME. The separator is glass fiber (GF / C), and C2032 button cells are assembled in a glove box filled with argon (Ar). The charge and discharge performance tests are carried out using the battery test system of Xinwei Electronics Co., Ltd.

[0045] S2: Button battery test voltage range is 0~3V, and 300mAh g -1 The current density was 1C and tests were conducted at 0.1C, 0.2C, 0.5C and 1C.

[0046] In this example, the material has a capacity of 241 mAh g at 0.1C test conditions. -1 The reversible capacity and ICE of 65% and 241 mAh g at 0.1C, 0.2C, 0.5C, and 1C rates are -1 , 136mAh g -1 、67mAh g -1 、35mAhg -1 reversible specific capacity.

[0047] From the attached Figure 1 It can be seen that the mass loss of the material is large before 400℃, so in order to ensure the final yield of the material, the pre-carbonization temperature is selected to be around 500℃.

[0048] From the attached Figure 2 It can be seen that the interlayer spacing of the samples prepared at different annealing times shifts to the right with the extension of time, resulting in a gradual decrease in the interlayer spacing and a decrease in the electrochemical performance.

[0049] From the attached Figure 3 It can be seen that as the annealing temperature increases, material I D / I G The decrease in the value means that the graphitization of the material increases, resulting in a decrease in the electrochemical performance of the material.

[0050] From the attached Figure 4 It can be seen that the electrochemical properties of the materials at different annealing temperatures are quite different. When the annealing temperature is 1100 °C, it has the best electrochemical performance, and its reversible specific capacity is 271 mAh g -1 , the initial effect is 70%.

[0051] From the attached Figure 5 It can be seen that the rate electrochemical performance of the samples prepared in different embodiments is quite different. Among them, the material prepared in Example 2 has the best electrochemical performance, with a capacity of 271 mAh g at the rates of 0.1C, 0.2C, 0.5C, and 1C. -1 , 246mAh g -1 , 147mAh g -1 , 89mAh g -1 reversible specific capacity.

[0052] From the attached Figure 6 It can be seen that there is no obvious difference in morphology between the samples prepared in different embodiments.

[0053] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a hard carbon negative electrode material derived from biomass, characterized in that: The following steps are involved: S1, pre-carbonizing the biomass material konjac flour to generate pre-carbonized material; S2, after the pre-carbonized material is cooled, it is subjected to ball milling, acid leaching, water washing and drying to obtain a hard carbon material precursor; S3, calcining the hard carbon material precursor at high temperature to obtain the hard carbon negative electrode material.

2. The method according to claim 1, characterized in that: In step S1, the pre-carbonization temperature is 200°C-800°C, and the time is 60min-300min.

3. The method according to claim 1, characterized in that: In step S2, the mass ratio of ball milling beads to pre-carbonized material is 60:1-10:1, the ball milling time is 2h-24h, and after ball milling, the material is passed through a 300-mesh sieve.

4. The method according to claim 1, characterized in that: In step S2, the acid leaching temperature is 25°C-100°C, and the time is 1h-24h; the acid used is at least one of hydrochloric acid, nitric acid, acetic acid, and phosphoric acid, and the concentration is 0.1-12 mol / L.

5. The method according to claim 1, characterized in that: In step S3, the heating rate is 1-10°C / min, the calcination temperature is 800-1500°C, and the calcination time is 30min-600min.

6. A biomass-derived hard carbon negative electrode material obtained by the method according to any one of claims 1 to 5.

7. Use of a biomass-derived hard carbon negative electrode material prepared by the method according to any one of claims 1 to 5 in a sodium ion battery.

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